The present invention relates to a nickel-metal hydride battery.
In general, nickel-metal hydride batteries, which have high energy density and excellent reliability, are widely used as power sources for portable devices and mobile devices and as power sources for electric vehicles and hybrid vehicles. A nickel-metal hydride battery includes a positive electrode of which the main component is nickel hydroxide, a negative electrode of which the main component is hydrogen absorbing alloy, and an alkali electrolyte solution.
When the nickel-metal hydride battery is charged and discharged, the hydrogen absorbing alloy absorbs and desorbs hydrogen. When hydrogen is repeatedly absorbed and desorbed, the hydrogen absorbing alloy expands and contracts. This pulverizes the hydrogen absorbing alloy. The pulverized hydrogen absorbing alloy is corroded by an alkali electrolyte solution. The corrosion advances as the surface area of the pulverized hydrogen absorbing alloy increases. This shortens the lifetime of the hydrogen absorbing alloy. A technique that limits the pulverization of the hydrogen absorbing alloy to improve the corrosion resistance of the hydrogen absorbing alloy against alkali electrolyte solution has been proposed in the prior art (for example, see Japanese Laid-Open Patent Publication No. 5-156382.